Our goal is to study the mechanisms of immune defense against tumors. More specifically we plan to carry out the following projects: (a) Studies on the biochemical mechanisms of macrophage activation. (b) Purification and characterization of a macrophage membrane associated cytotoxic factor. (c) Studies on the mechanisms of chemoattractive action of lysophosphatidylcholine on lymphocytes. (d) Studies on the mechanisms of action of lymphocyte activating factor. (e) Charcterization of monoclonal antibodies against human leukemia associated antigens.